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This Article Full Text Full Text (PDF) Supplemental Material All Versions of this Article: 106/5/1574    most recent 90744.2008v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Laveneziana, P. Articles by Scano, G. Search for Related Content PubMed PubMed Citation Articles by Laveneziana, P. Articles by Scano, G.

Effect of biventricular pacing on ventilatory and perceptual responses to exercise in patients with stable chronic heart failure

¹Department of Internal Medicine, Section of Immunology and Respiratory Medicine, University of Florence, Florence, Italy; ²Respiratory Investigation Unit, Department of Medicine, Queen's University, Kingston, Ontario, Canada; ³Centro Cardiologico Monzino, Istituto di Ricovero e Cura a Carattere Scientifico, Istituto di Cardiologia, University of Milan, Milan, Italy; ⁴Division of Cardiology, Clinica Medica Careggi, University of Florence, Florence, Italy; ⁵Department of Clinical Medicine, University "La Sapienza", Rome, Italy; and ⁶Department of Pulmonary Rehabilitation, Fondazione Don C. Gnocchi, Florence, Italy

Submitted 10 June 2008 ; accepted in final form 24 February 2009

Despite the growing evidence supporting the use of biventricular cardiac resynchronization therapy (CRT) in patients with chronic heart failure (CHF), the mechanisms whereby acute hemodynamic improvements lead to improved exertional dyspnea are not precisely known. We hypothesized that improved cardiac function and ventilation-perfusion relations following CRT would reduce ventilatory demand, thereby improving dynamic operating lung volumes and enhancing tidal volume expansion during exercise. This, in turn, would be expected to reduce perceived exertional dyspnea and contribute to improved exercise performance. In a randomized, double-blind, crossover study, we compared cardiovascular, metabolic, ventilatory responses (breathing pattern, operating lung volumes, pulmonary gas exchange) and exertional symptoms in seven stable CHF patients who undertook incremental cardiopulmonary cycle exercise test with CRT switched to the "on" (CRT_on) or "off" (CRT_off) modality. Following CRT_on, peak oxygen uptake was significantly increased by 15%, and dyspnea ratings were lower for a given work rate (at work rate of 40 W, dyspnea = 1 ± 0.4 vs. 2.5 ± 0.9 Borg units, P < 0.05) and ventilation (at ventilation of 31 l/min, dyspnea = 2 ± 0.7 vs. 3.3 ± 1.1 Borg units, P < 0.05). CRT_on was associated with improvements in ventilatory threshold, oxygen pulse, and oxygen uptake/work rate relationships (10.2 ± 1 vs. 7.9 ± 1.3 ml·min^–1·W^–1, P < 0.05). CRT_on reduced the ventilatory requirement during exercise as well as the steepness of ventilation-CO₂ production slope (35 ± 4 vs. 45 ± 7, P < 0.05). Changes in end-expiratory lung volume during exercise were less with CRT_on than with CRT_off (0.12 vs. 0.37 liter, P < 0.05), and breathing pattern was correspondingly slower and deeper. Biventricular pacing improved all noninvasive indexes of cardiac function and oxygen delivery during exercise. The decreased ventilatory demand, improved dynamic operating lung volumes, and the increased ability to expand tidal volume during exercise are potential factors in the reduction of exertional dyspnea.

heart failure; dyspnea; dynamic lung hyperinflation; ventilation; resynchronization